When, early in May, Pemberton began to feel the weight of Grant's pressure, he called on Gardner for reinforcements; thus Rust and Buford marched to the relief of Vicksburg on the 4th of May, Gregg followed on the 5th, and Maxey on the 8th. Miles was to have followed Maxey; in fact the preparations and orders had been given for the evacuation of Port Hudson; but now the same uncertainty and vacillation on the part of the Confederate chiefs that were to seal the doom of Vicksburg began to be felt at Port Hudson. Gardner, who had moved out with Maxey, had hardly arrived at Clinton when he was met by an order from Pemberton to return to Port Hudson with a few thousand men and to hold the place to the last. But ten days later, on the 19th of May, Johnston, who was then engaged in carrying out his own ideas, which differed radically from those of Davis and Pemberton, ordered Gardner to evacuate Port Hudson and to march on Jackson, Mississippi. This order, sent by courier as well as by telegraph, Gardner received just as Augur was marching from Baton Rouge to cut him off. Then it was too late, and when on the 23d Johnston peremptorily renewed his order for the evacuation, even the communication was closed.
The investment was made perfect by the presence in the river, above and below Port Hudson, of the ships and gunboats of the navy. Just above the place and at anchor around the bend lay the _Hartford_, now Commodore Palmer's flagship, with the _Albatross, Sachem, Estrella,_ and _Arizona_. Below, at anchor off Prophet's Island, were the _Monongahela_, bearing Farragut's flag, the _Richmond, Genesee, Essex_, and the mortar flotilla. Both the upper and the lower fleets watched the river at night by means of picket-boats in order to discover any movement and to intercept any communication with the garrison.
At the Hermitage plantation, on the west bank of the river, Benedict was stationed with his own regiment, the 162d New York, the 110th New York, and a section of artillery to prevent the escape of the Confederates by water. As soon as Weitzel joined, on the 25th of May, Banks began to close in his lines along the entire front. Weitzel moved up to the sugar-house on the telegraph road near the bridge over Foster's Creek; Paine advanced into the woods on Weitzel's left; Grover moved forward on the north of the Clinton Railway, crossed the ravine of Sandy Creek, and occupied the wooded rest of the steep hill in front. Augur prolonged the line across the Plains Store road under cover of the woods, yet in plain view of the Confederate entrenchments. Sherman held the Baton Rouge road, occupying the skirt of woods that formed the eastern edge of Slaughter's and Gibbons's fields.